A protozoan undergoes "binary fission" - with some help!

by Ron Neumeyer

 

These images, captured from video using a Snappy video grabber, illustrate the final stages of protozoan asexual reproduction (a process known as "binary fission"). The organism undergoing division, a small ciliate, gets a helping hand from one of its "cohorts" during the final stage, separation of the two daughter cells.

A second protozoan (lower centre) approaches the protozoan (centre) undergoing binary fission

The second protozoan forces it's way between the two daughter cells

Aiding the binary fission process in a rather unorthodox way!

Binary fission generally produces daughter cells with genetic material (DNA) identical to that of the parent. It is an efficient way for protozoa to increase in number during periods when environmental conditions are relatively stable. However, when environmental conditions begin to change, sexual reproduction generally becomes more prevalent. Sexual reproduction allows for the mixing of DNA among the various strains (asexual daughters) of a local protozoan population. Shuffling the deck in this manner produces cells which are genetically different from each other, an important characteristic as genetic make-up determines how cells respond to their environment. A genetically diverse population has more "options" in the face of changing conditions. In the biological world survival of the species is the ultimate objective. The more diverse a species gene pool, the greater the likelihood that it will persist.

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